Ternary photoinitiator system for curing of epoxy/polyol resin compositions

ABSTRACT

Photocurable, addition polymerizable compositions contain an epoxy resin and a photoinitiator system containing (a) an epoxy resin, (b) a hydroxyl containing material and (c) a photoinitiator system comprising: (i) an iodonium salt; (ii) a visible light sensitizer; and (iii) an electron donor compound, wherein the photoinitiator system has a photoinduced potential of at least about 100 mV relative to a standard solution of 2.9×10 -5  moles/g diphenyl iodonium hexafluoroantimonate and 1.5×10 -5  moles/g camphorquinone in 2-butanone. The compositions cure on exposure to light in the visible spectrum and are useful in a variety of applications, including dental adhesives and composites.

FIELD OF THE INVENTION

The invention relates to photocurable, addition polymerizablecompositions that contain an epoxy resin, a hydroxyl containingmaterial, and optionally a free radically polymerizable material. Thecompositions contain a ternary photoinitiator system that is activatedon exposure to actinic radiation in the visible spectrum. The inventionis additionally directed to methods of curing addition polymerizablecompositions using the ternary photoinitiator system.

BACKGROUND OF THE INVENTION

Epoxy containing compounds are known to be curable using variouscationic initiator systems. Smith, in U.S. Pat. No. 4,256,828, describesphotopolymerizable compositions that contain epoxides, an organiccompound with hydroxyl functionality, and a photosensitive aromaticsulfonium or iodonium salt of a halogen containing complex ion. Hayaseet al., U.S. Pat. No. 4,835,193, describes photopolymerizable epoxyresin compositions that comprise an epoxy resin and a heteropoly-acidaromatic sulfonium salt as the photocuring catalyst. In WO 95/14716Neckers et al. describe photohardenable compositions that comprise acationically polymerizable compound, a xanthene or fluorone dye, ahydrogen donor, and an onium salt. Palazzotto et al., U.S. Pat. No.5,545,676, describes addition polymerization of free-radicallypolymerizable materials. The photoinitiator system described in thatpatent comprises an aryliodonium salt, a sensitizer, and an electrondonor having an oxidation potential less than or equal to that ofp-dimethoxybenzene.

PCT published application No. WO 96/13538 describes a system for curingepoxy compounds by exposure to visible light by use of a systemcomprising an aryliodonium salt and a sensitizer. Comparative Example 34of this disclosure describes the use of one of the initiator systems ofPalazzotto et al., U.S. Pat. No. 5,545,676 in an epoxy/polyol resinsystem. N, N-dimethylbenzylamine is used as the electron donor. Theresults of this experiment indicated that the use of this amine donortended to retard the cure of the resin system.

Suppliers of cationically cured resins expressly warn against usingorganic amines in photoinitiated epoxy resins. An example of such awarning is found in Union Carbide literature regarding Cyracure®cycloaliphatic epoxides.

SUMMARY OF THE INVENTION

We have discovered, and the invention provides, a photopolymerizablecomposition that contains an epoxy resin, a hydroxyl-functional compoundand a photoinitiator system containing an iodonium salt, a visible lightsensitizer, and an electron donor compound, wherein the photoinitiatorsystem has a photoinduced potential greater than or equal to that of3-dimethylamino benzoic acid in a standard solution of 2.9×10⁻⁵ moles/gdiphenyl iodonium hexafluoroantimonate and 1.5×10⁻⁵ moles/gcamphorquinone in 2-butanone. Generally, 3-dimethylamino benzoic acid inthis standard exhibits a photoinduced potential of at least about 115 mVrelative to a standard solution of 2.9×10⁻⁵ moles/g diphenyl iodoniumhexafluoroantimonate and 1.5×10⁻⁵ moles/g camphorquinone in 2-butanone.

These compositions are curable on exposure to light having a wavelengthof about 400 to 1000 nm, and the invention provides a method of additionphotopolymerization comprising the step of irradiating aphotopolymerizable composition with light having a wavelength of about400 to 1000 nm until the composition gels or hardens, the compositioncontaining an epoxy resin, a hydroxyl-containing material and aphotoinitiator system containing an iodonium salt, a visible lightsensitizer, and an electron donor compound wherein the photoinitiatorsystem has a photoinduced potential of at least about 100 mV relative toa standard solution of 2.9×10⁻⁵ moles/g diphenyl iodoniumhexafluoroantimonate and 1.5×10⁻⁵ moles/g camphorquinone in 2-butanone.

In this application "polyol" and "hydroxyl-containing material" are usedinterchangeably.

The initiator systems of the invention allow efficient cationicpolymerization under conditions of room temperature and standardpressure. In addition, the initiator systems can, under appropriateconditions, initiate both cationic and free-radical polymerization. Thisproperty permits their use with a variety of photopolymerizablecompositions, including systems that contain acrylate or methacrylatefunctionality. Use of the initiator systems of the invention can providea substantial reduction in the time required for an epoxy and hydroxylcontaining resin composition to cure to a tack-free gel or solid. Thisreduction in gel time can represent about a 30 to 70% decrease in thetime required for a resin composition to harden to a tack-free gel orsolid.

DETAILED DESCRIPTION OF THE INVENTION

The photopolymerizable compositions of the invention are sensitivethroughout the visible spectral region and photocure without the need tointroduce substantial heat to the system to initiate cure, although anincidental amount of heat can be present. The term "visible light" isused throughout this application to refer to light having a wavelengthof about 400 to 1000 nanometers (nm). Photopolymerization of thecompositions takes place on exposure of the compositions to a source ofactinic radiation having a wavelength within this spectral region.

The cationically polymerizable epoxy resins useful in the compositionsof the invention are organic compounds having an oxirane ring, i.e., agroup of the formula ##STR1## which is polymerizable by ring opening.Such materials, broadly called epoxides, include monomeric epoxycompounds and epoxides of the polymeric type and can be aliphatic,cycloaliphatic, aromatic or heterocyclic. These materials generallyhave, on the average, at least 1 polymerizable epoxy group per molecule,preferably at least about 1.5 and more preferably at least about 2polymerizable epoxy groups per molecule. The polymeric epoxides includelinear polymers having terminal epoxy groups (e.g., a diglycidyl etherof a polyoxyalkylene glycol), polymers having skeletal oxirane units(e.g., polybutadiene polyepoxide), and polymers having pendent epoxygroups (e.g., a glycidyl methacrylate polymer or copolymer). Theepoxides may be pure compounds or may be mixtures of compoundscontaining one, two, or more epoxy groups per molecule. The "average"number of epoxy groups per molecule is determined by dividing the totalnumber of epoxy groups in the epoxy-containing material by the totalnumber of epoxy-containing molecules present.

These epoxy-containing materials may vary from low molecular weightmonomeric materials to high molecular weight polymers and may varygreatly in the nature of their backbone and substituent groups. Forexample, the backbone may be of any type and substituent groups thereoncan be any group that does not substantially interfere with cationiccure at room temperature. Illustrative of permissible substituent groupsinclude halogens, ester groups, ethers, sulfonate groups, siloxanegroups, nitro groups, phosphate groups, and the like. The molecularweight of the epoxy-containing materials may vary from about 58 to about100,000 or more.

Useful epoxy-containing materials include those which containcyclohexene oxide groups such as epoxycyclohexanecarboxylates, typifiedby 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate,3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexanecarboxylate, and bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate. For amore detailed list of useful epoxides of this nature, reference is madeto the U.S. Pat. No. 3,117,099, which is incorporated herein byreference.

Further epoxy-containing materials which are useful in the compositionsof this invention include glycidyl ether monomers of the formula##STR2## where R' is alkyl or aryl and n is an integer of 1 to 6.Examples are glycidyl ethers of polyhydric phenols obtained by reactinga polyhydric phenol with an excess of chlorohydrin such asepichlorohydrin (e.g., the diglycidyl ether of2,2-bis-(2,3-epoxypropoxyphenol)-propane). Further examples of epoxidesof this type are described in U.S. Pat. No. 3,018,262, which isincorporated herein by reference, and in "Handbook of Epoxy Resins" byLee and Neville, McGraw-Hill Book Co., New York (1967).

There are a host of commercially available epoxy resins which can beused in this invention. In particular, epoxides which are readilyavailable include octadecylene oxide, epichlorohydrin, styrene oxide,vinyl cyclohexene oxide, glycidol, glycidylmethacrylate, diglycidylether of Bisphenol A (e.g., those available under the trade designations"Epon 828", "Epon 825", "Epon 1004" and "Epon 1010" from Shell ChemicalCo., "DER-331", "DER-332", and "DER-334", from Dow Chemical Co.),vinylcyclohexene dioxide (e.g., "ERL-4206" from Union Carbide Corp.),3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate (e.g.,"ERL-4221" or "CYRACURE UVR 6110" or UVR 6105" from Union CarbideCorp.), 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexenecarboxylate (e.g., "ERL-4201" from Union Carbide Corp.),bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate (e.g., "ERL-4289" fromUnion Carbide Corp.), bis(2,3-epoxycyclopentyl) ether (e.g., "ERL-0400"from Union Carbide Corp.), aliphatic epoxy modified from polypropyleneglycol (e.g., "ERL-4050" and "ERL-4052" from Union Carbide Corp.),dipentene dioxide (e.g., "ERL-4269" from Union Carbide Corp.),epoxidized polybutadiene (e.g., "Oxiron 2001" from FMC Corp.), siliconeresin containing epoxy functionality, flame retardant epoxy resins(e.g., "DER-580", a brominated bisphenol type epoxy resin available fromDow Chemical Co.), 1,4-butanediol diglycidyl ether of phenolformaldehydenovolak (e.g., "DEN-431" and "DEN-438" from Dow Chemical Co.), andresorcinol diglycidyl ether (e.g., "Kopoxite" from Koppers Company,Inc.), bis(3,4-epoxycyclohexyl)adipate (e.g., "ERL-4299" or "UVR-6128",from Union Carbide Corp.), 2-(3,4-epoxycyclohexyl-5, 5-spiro-3,4-epoxy)cyclohexane-meta-dioxane (e.g., "ERL-4234" from Union Carbide Corp.),vinylcyclohexene monoxide 1,2-epoxyhexadecane (e.g., "UVR-6216" fromUnion Carbide Corp.), alkyl glycidyl ethers such as alkyl C₈ -C₁₀glycidyl ether (e.g., "HELOXY Modifier 7" from Shell Chemical Co.),alkyl C₁₂ -C₁₄ glycidyl ether (e.g., "HELOXY Modifier 8" from ShellChemical Co.), butyl glycidyl ether (e.g., "HELOXY Modifier 61" fromShell Chemical Co.), cresyl glycidyl ether (e.g., "HELOXY Modifier 62"from Shell Chemical Co.), p-ter butylphenyl glycidyl ether (e.g.,"HELOXY Modifier 65" from Shell Chemical Co.), polyfunctional glycidylethers such as diglycidyl ether of 1,4-butanediol (e.g., "HELOXYModifier 67" from Shell Chemical Co.), diglycidyl ether of neopentylglycol (e.g., "HELOXY Modifier 68" from Shell Chemical Co.), diglycidylether of cyclohexanedimethanol (e.g., "HELOXY Modifier 107" from ShellChemical Co.), trimethylol ethane triglycidyl ether (e.g., "HELOXYModifier 44" from Shell Chemical Co.), trimethylol propane triglycidylether (e.g., "HELOXY Modifier 48" from Shell Chemical Co.), polyglycidylether of an aliphatic polyol (e.g., "HELOXY Modifier 84" from ShellChemical Co.), polyglycol diepoxide (e.g., "HELOXY Modifier 32" fromShell Chemical Co.), bisphenol F epoxides (e.g., "EPN-1138" or "GY-281"from Ciba-Geigy Corp.), 9,9-bis[4-(2,3-epoxypropoxy)-phenyl]fluorenone(e.g., "Epon 1079" from Shell Chemical Co.).

Still other epoxy resins contain copolymers of acrylic acid esters orglycidol such as glycidylacrylate and glycidylmethacrylate with one ormore copolymerizable vinyl compounds. Examples of such copolymers are1:1 styrene-glycidylmethacrylate, 1:1methylmethacrylate-glycidylacrylate and a 62.5:24:13.5methylmethacrylate-ethyl acrylate-glycidylmethacrylate.

Other useful epoxy resins are well known and contain such epoxides asepichlorohydrins, alkylene oxides, e.g., propylene oxide, styrene oxide;alkenyl oxides, e.g., butadiene oxide; glycidyl esters, e.g., ethylglycidate.

The polymers of the epoxy resin can optionally contain otherfunctionalities that do not substantially interfere with cationic cureat room temperature.

Blends of various epoxy-containing materials are also contemplated inthis invention. Examples of such blends include two or more weightaverage molecular weight distributions of epoxy-containing compounds,such as low molecular weight (below 200), intermediate molecular weight(about 200 to 10,000) and higher molecular weight (above about 10,000).Alternatively or additionally, the epoxy resin may contain a blend ofepoxy-containing materials having different chemical natures, such asaliphatic and aromatic, or functionalities, such as polar and non-polar.Other cationically polymerizable polymers can additionally beincorporated, such as vinyl ethers, etc., if desired.

The hydroxyl-containing material which is used in the present inventioncan be any organic material having hydroxyl functionality of at least 1,and preferably at least 2.

Preferably the hydroxyl-containing material contains two or more primaryor secondary aliphatic hydroxyl groups (i.e., the hydroxyl group isbonded directly to a non-aromatic carbon atom). The hydroxyl groups canbe terminally situated, or they can be pendent from a polymer orcopolymer. The molecular weight of the hydroxyl-containing organicmaterial can vary from very low (e.g., 32) to very high (e.g., onemillion or more). Suitable hydroxyl-containing materials can have lowmolecular weights, i.e. from about 32 to 200, intermediate molecularweight, i.e. from about 200 to 10,000, or high molecular weight, i.e.above about 10,000. As used herein, all molecular weights are weightaverage molecular weights.

The hydroxyl-containing material can optionally contain otherfunctionalities that do not substantially interfere with cationic cureat room temperature. Thus, the hydroxyl-containing materials can benonaromatic in nature or can contain aromatic functionality. Thehydroxyl-containing material can optionally contain heteroatoms in thebackbone of the molecule, such as nitrogen, oxygen, sulfur, and thelike, provided that the ultimate hydroxyl-containing material does notsubstantially interfere with cationic cure at room temperature. Thehydroxyl-containing material can, for example, be selected fromnaturally occurring or synthetically prepared cellulosic materials. Ofcourse, the hydroxyl-containing material is also substantially free ofgroups which may be thermally or photolytically unstable; that is, thematerial will not decompose or liberate volatile components attemperatures below about 100° C. or in the presence of actinic lightwhich may be encountered during the desired curing conditions for thephotocopolymerizable composition.

Representative examples of suitable hydroxyl-containing materials havinga hydroxyl functionality of 1 include alkanols, monoalkyl ethers ofpolyoxyalkyleneglycols, monoalkyl ethers of alkylene-glycols, and othersknown in the art.

Representative examples of useful monomeric polyhydroxy organicmaterials include alkylene glycols (e.g., 1,2-ethanediol;1,3-propanediol; 1,4-butanediol; 1,6-hexanediol; 1,8-octanediol;2-ethyl-1,6-hexanediol; bis(hydroxymethyl)cyclohexane;1,18-dihydroxyoctadecane; 3-chloro-1,2-propanediol); polyhydroxyalkanes(e.g., glycerine, tri-methylolethane, pentaerythritol, sorbitol) andother polyhydroxy compounds such as N,N--bis(hydroxyethyl)benzamide;2-butyne-1,4-diol; 4,4-bis(hydroxymethyl)diphenylsulfone; castor oil;and the like.

Representative examples of useful polymeric hydroxyl-containingmaterials include polyoxyethylene and polyoxypropylene glycols, andparticularly the polyoxyethylene and polyoxypropylene glycol diols andtriols having molecular weights from about 200 to about 10,000corresponding to a hydroxy equivalent weight of 100 to 5000 for thediols or 70 to 3300 for triols; polytetramethylene ether glycols such aspolytetrahydrofuran or "poly THF" of varying molecular weight;copolymers of hydroxypropyl and hydroxyethyl acrylates and methacrylateswith other free radical-polymerizable monomers such as acrylate esters,vinyl halides, or styrene; copolymers containing pendent hydroxy groupsformed by hydrolysis or partial hydrolysis of vinyl acetate copolymers,polyvinylacetal resins containing pendent hydroxyl groups; modifiedcellulose polymers such as hydroxyethylated and hydroxypropylatedcellulose; hydroxy-terminated polyesters; hydroxy-terminatedpolylactones, and particularly the polycaprolactones; fluorinatedpolyoxyethylene or polyoxypropylene glycols; and hydroxy-terminatedpolyalkadienes.

Useful commercially available hydroxyl-containing materials include the"TERATHANE" series of polytetramethylene ether glycols such as"TERATHANE" 650, 1000, 2000 and 2900 (available from du Pont de Nemours,Wilmington, Del.) the "PEP" series of polyoxyalkylene tetrols havingsecondary hydroxyl groups such as "PEP" 450, 550 and 650; "BUTVAR"series of polyvinylacetal resins such as "BUTVAR" B-72A, B-73, B-76,B-90 and B-98 (available from Monsanto Chemical Company, St. Louis,Mo.); and the "FORMVAR" series of resins such as 7/70, 12/85, 7/95S,7/95E, 15/95S and 15/95E (available from Monsanto Chemical Company); the"TONE" series of polycaprolactone polyols such as "TONE" 0200, 0210,0230,0240, 0300 and 0301 (available from Union Carbide); "PARAPLEXU-148" aliphatic polyester diol (available from Rohm and Haas,Philadelphia, Pa.), the "MULTRON" R series of saturated polyesterpolyols such as "MULTRON" R-2, R-12A, R-16, R-18, R-38, R-68 and R-74(available from Mobay Chemical Co.); "KLUCEL E" hydroxypropylatedcellulose having an equivalent weight of approximately 100 (availablefrom Hercules Inc.); "Alcohol Soluble Butyrate" cellulose acetatebutyrate ester having a hydroxyl equivalent weight of approximately 400(available from Eastman Kodak Co., Rochester, N.Y.); polyether polyolssuch as polypropylene glycol diol (e.g., "ARCOL PPG-425", "ArcolPPG-725", "ARCOL PPG-1025", "ARCOL PPG-2025", ARCOL PPG-3025", "ARCOLPPG-4025" from ARCO Chemical Co.); polypropylene glycol triol (e.g.,"ARCOL LT-28", "ARCOL LHT-42", "ARCOL LHT 112", "ARCOL LHT 240", "ARCOLLG-56", "ARCOL LG-168", "ARCOL LG-650" from ARCO Chemical Co.); ethyleneoxide capped polyoxypropylene triol or diol (e.g., "ARCOL 11-27", "ARCOL11-34", "ARCOL E-351", "ARCOL E-452", "ARCOL E-785", "ARCOL E-786" fromARCO Chemical Co.); ethoxylated bis-phenol A; propylene oxide orethylene oxide-based polyols (e.g., "VORANOL" polyether polyols from theDow Chemical Co.).

The amount of hydroxyl-containing organic material used in thecompositions of the invention may vary over broad ranges, depending uponfactors such as the compatibility of the hydroxyl-containing materialwith the epoxide, the equivalent weight and functionality of thehydroxyl-containing material, the physical properties desired in thefinal cured composition, the desired speed of photocure, and the like.

Blends of various hydroxyl-containing materials are particularlycontemplated in this invention. Examples of such blends include two ormore molecular weight distributions of hydroxyl-containing compounds,such as low molecular weight (below 200), intermediate molecular weight(about 200 to 10,000) and higher molecular weight (above about 10,000).Alternatively or additionally, the hydroxyl-containing material cancontain a blend of hydroxyl-containing materials having differentchemical natures, such as aliphatic and aromatic, or functionalities,such as polar and non-polar. As an additional example, one may usemixtures of two or more poly-functional hydroxy materials or one or moremono-functional hydroxy materials with poly-functional hydroxymaterials.

If desired, the composition can also contain a free-radicallypolymerizable material, including one or more ethylenically unsaturatedmonomer, monomers, oligomers or polymers. Suitable materials contain atleast one ethylenically unsaturated bond, and are capable of undergoingaddition polymerization. Such free radically polymerizable materialsinclude mono-, di- or poly- acrylates and methacrylates such as methylacrylate, methyl methacrylate, ethyl acrylate, isopropyl methacrylate,n-hexyl acrylate, stearyl acrylate, allyl acrylate, glycerol diacrylate,glycerol triacrylate, ethyleneglycol diacrylate, diethyleneglycoldiacrylate, triethyleneglycol dimethacrylate, 1,3-propanedioldiacrylate, 1,3-propanediol dimethacrylate, trimethylolpropanetriacrylate, 1,2,4-butanetriol trimethacrylate, 1,4-cyclohexanedioldiacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate,pentaerythritol tetramethacrylate, sorbitol hexacrylate,bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylmethane,bis[l-(3-acryloxy-2-hydroxy)]-p-propoxyphenyldimethylmethane, andtrishydroxyethyl-isocyanurate trimethacrylate; the bis-acrylates andbis-methacrylates of polyethylene glycols of molecular weight 200-500,copolymerizable mixtures of acrylated monomers such as those in U.S.Pat. No. 4,652,274, and acrylated oligomers such as those of U.S. Pat.No. 4,642,126; and vinyl compounds such as styrene, diallyl phthalate,divinyl succinate, divinyl adipate and divinylphthalate. Mixtures of twoor more of these free radically polymerizable materials can be used ifdesired.

If desired, the polymerizable material(s) may contain both epoxy andfree-radically polymerizable functionalities in a single molecule. Thesemay be obtained by reacting a di- or poly-epoxide with one or moreequivalents of an ethylenically unsaturated carboxylic acid. An exampleof such a material is the reaction product of UVR-6105 (available fromUnion Carbide) with one equivalent of methacrylic acid. Commerciallyavailable materials having epoxy and free-radically polymerizablefunctionalities include the "Cyclomer" series, such as Cyclomer M100 orM101, available from Daicel Chemical, Japan.

The polymerizable material(s) can also contain hydroxyl and freeradically polymerizable functionalities in a single molecule. Examplesof such materials include hydroxyalkylacrylates andhydroxyalkylmethacrylates such as hydroxyethylacrylate,hydroxyethylmethacrylate; glycerol mono- or di-acrylate andmethacrylate; and the like.

The epoxy resin, hydroxyl-containing material and optional freeradically polymerizable material(s) are combined with a three componentor ternary photoinitiator system. Three component initiator systems aredescribed in Palazzotto et al., U.S. Patent No. 5,545,676, which isincorporated herein by reference. The first component in thephotoinitiator system is an iodonium salt, i.e., a diaryliodonium salt.The iodonium salt should be soluble in the monomer and preferably isshelf-stable, meaning it does not spontaneously promote polymerizationwhen dissolved therein in the presence of the sensitizer and donor.Accordingly, selection of a particular iodonium salt may depend to someextent upon the particular monomer, sensitizer and donor chosen.Suitable iodonium salts are described in U.S. Pat. Nos. 3,729,313,3,741,769, 3,808,006, 4,250,053 and 4,394,403, the iodonium saltdisclosures of which are incorporated herein by reference. The iodoniumsalt can be a simple salt, containing an anion such as Cl⁻, Br⁻, I⁻ orC₄ H₅ SO₃ ⁻ ; or a metal complex salt containing an antimonate,arsenate, phosphate or borate such as SbF₅ OH⁻ or AsF₆ ⁻. Mixtures ofiodonium salts can be used if desired.

Examples of useful aromatic iodonium complex salt photoinitiatorsinclude: diphenyliodonium tetrafluoroborate; di(4-methylphenyl)iodoniumtetrafluoroborate; phenyl-4-methylphenyliodonium tetrafluoroborate;di(4-heptylphenyl)iodonium tetrafluoroborate; di(3-nitrophenyl)iodoniumhexafluorophosphate; di(4-chlorophenyl)iodonium hexafluorophosphate;di(naphthyl)iodonium tetrafluoroborate;di(4-trifluoromethylphenyl)iodonium tetrafluoroborate; diphenyliodoniumhexafluorophosphate; di(4-methylphenyl)iodonium hexafluorophosphate;diphenyliodonium hexafluoroarsenate; di(4-phenoxyphenyl)iodoniumtetrafluoroborate; phenyl-2-thienyliodonium hexafluorophosphate;3,5-dimethylpyrazolyl-4-phenyliodonium hexafluorophosphate;diphenyliodonium hexafluoroantimonate; 2,2'-diphenyliodoniumtetrafluoroborate; di(2,4-dichlorophenyl)iodonium hexafluorophosphate;di(4-bromophenyl)iodonium hexafluorophosphate;di(4-methoxyphenyl)iodonium hexafluorophosphate;di(3-carboxyphenyl)iodonium hexafluorophosphate;di(3-methoxycarbonylphenyl)iodonium hexafluorophosphate;di(3-methoxysulfonylphenyl)iodonium hexafluorophosphate;di(4-acetamidophenyl)iodonium hexafluorophosphate;di(2-benzothienyl)iodonium hexafluorophosphate; and diphenyliodoniumhexafluoroantimonate.

Of the aromatic iodonium complex salts which are suitable for use in thecompositions of the invention diaryliodonium hexafluorophosphate anddiaryliodonium hexafluoroantimonate are among the preferred salts. Thesesalts are preferred because, in general, they promote faster reaction,and are more soluble in inert organic solvents than are other aromaticiodonium salts of complex ions.

The aromatic iodonium complex salts may be prepared by metathesis ofcorresponding aromatic iodonium simple salts (such as, for example,diphenyliodonium bisulfate) in accordance with the teachings of Beringeret al., J. Am. Chem. Soc. 81,342 (1959). Thus, for example, the complexsalt diphenyliodonium tetrafluoroborate is prepared by the addition at60° C. of an aqueous solution containing 29.2 g silver fluoroborate, 2 gfluoroboric acid, and 0.5 g phosphorous acid in about 30 ml of water toa solution of 44 g (139 millimoles) of diphenyliodonium chloride. Thesilver halide that precipitates is filtered off and the filtrateconcentrated to yield diphenyliodonium fluoroborate which may bepurified by recrystallization.

The aromatic iodonium simple salts may be prepared in accordance withBeringer et al., above, by various methods including (1) coupling of twoaromatic compounds with iodyl sulfate in sulfuric acid, (2) coupling oftwo aromatic compounds with an iodate in acetic acid-aceticanhydride-sulfuric acid, (3) coupling of two aromatic compounds with aniodine acrylate in the presence of an acid, and (4) condensation of aniodoso compound, an iodoso diacetate, or an iodoxy compound with anotheraromatic compound in the presence of an acid. Diphenyliodonium bisulfateis prepared by method (3), for example, by the addition over a period ofeight hours at below 5° C. of a mixture of 35 ml of conc. sulfuric acidand 50 ml of acetic anhydride to a well-stirred mixture of 55.5 ml ofbenzene, 50 ml of acetic anhydride, and 53.5 g of potassium iodate. Themixture is stirred for an additional four hours at 0°-5° C. and at roomtemperature (about 25° C.) for 48 hours and treated with 300 ml ofdiethyl ether. On concentration, crude diphenyliodonium bisulfateprecipitates and may be purified by recrystallization if desired.

The second component in the photoinitiator system is the sensitizer. Thesensitizer should be soluble in the photopolymerizable composition, freeof functionalities that would substantially interfere with the cationiccuring process, and capable of light absorption within the range ofwavelengths between about 300 and about 1000 nanometers.

Suitable sensitizers include compounds in the following categories:ketones, coumarin dyes (e.g., ketocoumarins), xanthene dyes, acridinedyes, thiazole dyes, thiazine dyes, oxazine dyes, azine dyes,aminoketone dyes, porphyrins, aromatic polycyclic hydrocarbons,p-substituted aminostyryl ketone compounds, aminotriaryl methanes,merocyanines, squarylium dyes and pyridinium dyes. Ketones (e.g.,monoketones or alpha-diketones), ketocoumarins, aminoarylketones andp-substituted aminostyryl ketone compounds are preferred sensitizers.For applications requiring deep cure (e.g., cure of highly-filledcomposites), it is preferred to employ sensitizers having an extinctioncoefficient below about 1000 lmole⁻¹ cm⁻¹, more preferably about orbelow 100 lmole⁻¹ cm⁻¹, at the desired wavelength of irradiation forphotopolymerization. The alpha-diketones are an example of a class ofsensitizers having this property, and are particularly preferred fordental applications.

By way of example, a preferred class of ketone sensitizers has theformula:

    ACO(X).sub.b B

where X is CO or CR¹ R² where R¹ and R² can be the same different, andcan be hydrogen, alkyl, alkaryl or aralkyl, b is zero, and A and B canbe the same or different and can be substituted (having one or morenon-interfering substituents) or unsubstituted aryl, alkyl, alkaryl, oraralkyl groups, or together A and B can form a cyclic structure whichcan be a substituted or unsubstituted cycloaliphatic, aromatic,heteroaromatic or fused aromatic ring.

Suitable ketones of the above formula include monoketones (b=0) such as2,2-, 4,4- or 2,4-dihydroxybenzophenone, di-2-pyridyl ketone,di-2-furanyl ketone, di-2-thiophenyl ketone, benzoin, fluorenone,chalcone, Michler's ketone, 2-fluoro-9-fluorenone, 2-chlorothioxanthone,acetophenone, benzophenone, 1- or 2-acetonaphthone, 9-acetylanthracene,2-, 3- or 9-acetylphenanthrene, 4-acetylbiphenyl, propiophenone,n-butyrophenone, valerophenone, 2-, 3- or 4-acetylpyridine,3-acetylcoumarin and the like. Suitable diketones includearalkyldiketones such as anthraquinone, phenanthrenequinone, o-, m- andp-diacetylbenzene, 1,3-, 1,4-, 1,5-, 1,6-, 1,7- and1,8-diacetylnaphthalene, 1,5-, 1,8- and 9,10-diacetylanthracene, and thelike. Suitable I-diketones (b=1 and X=CO) include 2,3-butanedione,2,3-pentanedione, 2,3-hexanedione, 3,4-hexanedione, 2,3-heptanedione,3,4-heptanedione, 2,3-octanedione, 4,5-octanedione, benzil, 2,2'-3 3'-and 4,4'-dihydroxylbenzil, furil, di-3,3'-indolylethanedione,2,3-bornanedione (camphorquinone), biacetyl, 1,2-cyclohexanedione,1,2-naphthaquinone, acenaphthaquinone, and the like.

Examples of particularly preferred visible light sensitizers includecamphorquinone; glyoxal; biacetyl; 3,3,6,6-tetramethylcyclohexanedione;3,3,7,7-tetramethyl-1,2-cycloheptanedione;3,3,8,8-tetramethyl-1,2-cyclooctanedione;3,3,18,18-tetramethyl-1,2-cyclooctadecanedione; dipivaloyl; benzil;furil; hydroxybenzil; 2,3-butanedione; 2,3-pentanedione;2,3-hexanedione; 3,4-hexanedione; 2,3-heptanedione; 3,4-heptanedione;2,3-octanedione; 4,5-octanedione; and 1,2-cyclohexanedione. Of these,camphorquinone is the most highly preferred sensitizer.

The third component of the initiator system is an electron donor. Theelectron donor compound(s) should meet the requirements set forth belowand be soluble in the polymerizable composition. The donor can also beselected in consideration of other factors, such as shelf stability andthe nature of the polymerizable materials, iodonium salt and sensitizerchosen. A class of donor compounds that may be useful in the inventivesystems may be selected from some of the donors described in Palazzottoet al., U.S. Pat. No. 5,545,676. Possible donor compounds that meet thecriteria set forth by Palazzotto et al. must then be tested using one orboth of the methods set forth below to determine if they will be usefuldonors for the photopolymerizable compositions of the invention.

The donor is typically an alkyl aromatic polyether or an alkyl, arylamino compound wherein the aryl group is substituted by one or moreelectron withdrawing groups. Examples of suitable electron withdrawinggroups include carboxylic acid, carboxylic acid ester, ketone, aldehyde,sulfonic acid, sulfonate and nitrile groups.

The suitability of a compound for use as an electron donor in thecompositions of the invention may be determined by measuring thephotoinduced potential of a sample photoinitiator system that includesthe compound. The photoinduced potential can be evaluated in thefollowing manner. A standard solution is prepared that contains 2.9×10⁻⁵moles/g of diphenyl iodonium hexafluoroantimonate and 1.5×10⁻⁵ moles/gof camphorquinone in 2-butanone. A pH electrode is then immersed in thesolution and a pH meter is calibrated to zero mV. A test solution of thestandard solution and the compound is prepared next using the compoundat a concentration of 2.9×10⁻⁵ moles/g. This test solution is irradiatedusing blue light having a wavelength of about 400 to 500 nm having anintensity of about 200 to 400 mW/cm² for about 5 to 10 seconds at adistance of about 1 mm. Millivolts relative to the standard solution arethen determined by immersing the pH electrode in the test solution andobtaining a mV reading on the pH meter. Useful donors are thosecompounds that provide a reading of at least 100 mV relative to thestandard solution, and preferably provide a gel time for thecompositions that is at least about 30 to 40 percent shorter than forcompositions that do not contain the donor. Higher mV readings aregenerally indicative of greater activity.

In some instances there may be some uncertainty regarding the outcome ofthe above procedure. This may be due to questions or uncertainty arisingfrom the instrumentation employed, from the way the procedure wascarried out, or other factors, or one may wish to verify the suitabilityof a particular compound. A second test may be performed to verify theresult obtained by following the above procedure and resolve any suchuncertainty.

The second method involves the evaluation of the photoinduced potentialof an initiator system that includes the compound compared to a systemthat includes 3-dimethylanino benzoic acid. For this method, a standardsolution of 2.9×10⁻⁵ moles/g diphenyl iodonium hexafluoroantimonate,1.5×10⁻⁵ moles/g camphorquinone and 2.9×10⁻⁵ moles/g of3-dimethylaminobenzoic acid in 2-butanone is prepared. A pH electrode isthen immersed in the solution and a pH meter is calibrated to zero mV.The standard solution is irradiated with blue light having a wavelengthof between about 400-500 nm and an intensity of about 200 to 400 mW/cm²for about 5 to 10 seconds using a focused light source such as a dentalcuring light at a distance of about 1 mm. After light exposure, thepotential of the solution is measured by immersing a pH electrode in theirradiated standard solution and reading the potential in mV using a pHmeter. A test solution is then prepared using 2.9×10⁻⁵ moles/g ofdiphenyl iodonium hexafluoroantimonate, 1.5×10⁻⁵ moles/g ofcamphorquinone and 2.9×10⁻⁵ moles/g of the compound in 2-butanone. Thetest solution is irradiated and the photoinduced potential measuredusing the same technique as described for the standard solution. If thetest solution has a photoinduced potential that is the same as orgreater than that of the 3-dimethylaminobenzoic acid containing standardsolution, then the compound is a useful donor.

A preferred group of alkyl, aryl amine donor compounds is described bythe following structural formula: ##STR3## wherein R¹ is independently Hor C₁₋₁₈ is alkyl that is optionally substituted by one or more halogen,--CN, --OH, --SH, C₁₋₁₈ alkoxy, C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl,COOH, COOC₁₋₁₈ alkyl, (C₁₋₁₈ alkyl)₀₋₁ -CO--C₁₋₁₈ alkyl or SO₃ R² arylthat is optionally substituted by one or more electron withdrawing groupwhere R² is H; C₁₋₁₈ alkyl that is optionally substituted by one or morehalogen, --CN, --OH, --SH, C₁₋₁₈ alkoxy, C₁₋₁₈ alkylthio, C₃₋₁₈cycloalkyl, aryl, COOH, COOC₁₋₁₈ alkyl, (C₁₋₁₈ alkyl)₀₋₁ -CO--C₁₋₁₈alkyl or SO₃ H, or the R¹ groups may be joined to form a ring, and Ar isaryl that is substituted by one or more electron withdrawing groups.Suitable electron withdrawing groups include--COOH, --COOR², --SO₃ R²,--CN, --CO--C₁₋₁₈ alkyl and --C(O)H groups. Preferably, the aryl groupis substituted by one or more carboxylic acid, carboxylic acid ester,ketone, alkehyde, sulfonic acid, sulfonate, or nitrile groups.

A preferred group of aryl alkyl polyethers has the following structuralformula: ##STR4## wherein n=1-3 each R₃ is independently H or C₁₋₁₈alkyl that is optionally substituted by one or more halogen, --CN, --OH,--SH, C₁₋₁₈ alkoxy, C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl, substitutedaryl, --COOH, --COOC₁˜ alkyl, --(C₁₋₁₈ alkyl)₀₋₁ -COH, --(C₁₋₁₈alkyl)₀₋₁ -CO--C₁₋₁₈ alkyl, --CO--C₁₋₁₈ alkyl, --C(O)H or --C₂₋₁₈alkenyl groups or the R³ groups together my form a ring and each R₄ canbe C₁₋₁₈ alkyl that is optionally substituted by one or more halogen,--CN, --OH, --SH, C₁₋₁₈ alkoxy, C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl,substituted aryl, --COOH, --COOC₁₋₁₈ alkyl, --(C₁₋₁₈ alkyl)₀₋₁ -COH,--(C₁₋₁₈ alkyl)₀₋₁ -CO --C₁₋₁₈ alkyl, --CO--C₁₋₁₈ alkyl, --C(O)H or--C₂₋₁₈ alkenyl groups.

In each of the above formulas the alkyl groups can be straight-chain orbranched, and the cycloalkyl group preferably has 3 to 6 ring carbonatoms but may have additional alkyl substitution up to the specifiednumber of carbon atoms. The aryl groups may be carbocyclic orheterocyclic aryl, but are preferably carbocyclic and more preferablyphenyl rings.

Preferred donor compounds include 4-dimethylaminobenzoic acid, ethyl4-dimethylaminobenzoate, 3-dimethylaminobenzoic acid,4-dimethylaminobenzoin, 4-dimethylaminobenzaldehyde,4-dimethylaminobenzonitrile and 1,2,4-trimethoxybenzene.

The photoinitiator compounds are provided in an amount effective toinitiate or enhance the rate of cure of the resin system. It has beenfound that the amount of donor that is used can be critical particularlywhen the donor is an amine. Too much donor can be deleterious to cureproperties. Preferably, the sensitizer is present in about 0.05-5 weightpercent based on resin compounds of the overall composition. Morepreferably, the sensitizer is present at 0.10-1.0 weight percent.Similarly, the iodonium initiator is preferably present at 0.05-10.0weight percent, more preferably at 0.10-5.0 weight percent, and mostpreferably 0.50-3.0 weight percent. Likewise, the donor is preferablypresent at 0.01-5.0 weight percent, more preferably 0.05-1.0 weightpercent, and most preferably 0.05-0.50 weight percent.

The photopolymerizable compositions of the invention are prepared bysimply admixing, under "safe light" conditions, the components of theinventive compositions. Suitable inert solvents may be employed ifdesired when effecting this mixture. Any solvent may be used which doesnot react appreciably with the components of the inventive compositions.Examples of suitable solvents include acetone, dichloromethane, andacetonitrile. A liquid material to be polymerized may be used as asolvent for another liquid or solid material to be polymerized.Solventless compositions can be prepared by simply dissolving thearomatic iodonium complex salt and sensitizer in the epoxy resin polyolmixture with or without the use of mild heating to facilitatedissolution.

The compositions of the present invention provide a very usefulcombination of cure speed, cure depth and shelf life. They cure welleven when loaded with large amounts of fillers, and can be used in avariety of applications including graphic arts imaging (e.g. for colorproofing systems, curable inks, or silverless imaging), printing plates(e.g. projection plates or laser plates), photoresists, solder masks,electronic conformal coatings, coated abrasives, magnetic media,photocurable adhesives (e.g. for orthodontics) and photocurablecomposites (e.g., for autobody repair or dentistry).

Dental applications particularly benefit from the unique compositions ofthe present invention. Until now, acrylate and methacrylate chemistryhas been used extensively for adhesive and restorative dentalcompositions. This chemistry has the advantage of being curable withvisible light using photoinitiator systems, but has the disadvantage ofundergoing a relatively high degree of shrinkage during thepolymerization process. In contrast, during polymerization the epoxyresins found in the compositions of the present invention shrinksignificantly less than the acrylate and methacrylate resins of theprior art. The present invention provides a system for curingepoxy/polyol resin systems, with or without the presence of an acrylateor methacrylate in an acceptable time frame and to a sufficient depthusing visible light source equipment already available in the dentaloffice.

The dental materials may be filled or unfilled and include dentalmaterials such as direct esthetic restorative materials (e.g., anteriorand posterior restoratives), prostheses, adhesives and primers for oralhard tissues, sealants, veneers, cavity liners, orthodontic bracketadhesives for use with any type of bracket (such as metal, plastic andceramic), crown and bridge cements, artificial crowns, artificial teeth,dentures, and the like. These dental materials are used in the mouth andare disposed adjacent to natural teeth. The phrase "disposed adjacentto" as used herein refers to the placing of a dental material intemporary or permanent bonding (e.g., adhesive) or touching (e.g.,occlusal or proximal) contact with a natural tooth. The term "composite"as used herein refers to a filled dental material. The term"restorative" as used herein refers to a composite which is polymerizedafter it is disposed adjacent to a tooth. The term "prosthesis" as usedherein refers to a composite which is shaped and polymerized for itsfinal use (e.g., as crown, bridge, veneer, inlay, onlay or the like)before it is disposed adjacent to a tooth. The term "sealant" as usedherein refers to a lightly filled composite or to an unfilled dentalmaterial which is cured after it is disposed adjacent to a tooth."Polymerizable" refers to curing or hardening the dental material, e.g.,by free-radical, cationic or mixed reaction mechanisms.

In certain applications, the use of a filler may be appropriate. Thechoice of filler affects important properties of the composite such asits appearance, radiopacity and physical and mechanical properties.Appearance is affected in part by adjustment of the amounts and relativerefractive indices of the ingredients of the composite, thereby allowingalteration of the translucence, opacity or pearlescence of thecomposite. Epoxy resin compositions of the invention, either alone or inadmixture with diluent monomer, can be prepared with refractive indiceswhich approach or approximate the refractive indices of fillers such asquartz (refractive index 1.55), submicron silica (refractive index1.46), and 5.5:1 mole ratio SiO:ZrO, non-vitreous microparticles(refractive index 1.54). In this way the appearance of the dentalmaterial can, if desired, be made to closely approximate the appearanceof natural dentition.

Radiopacity is a measurement of the ability of the composite to bedetected by x-ray examination. Frequently a radiopaque composite will bedesirable, for instance, to enable the dentist to determine whether ornot a dental restoration remains sound. Under other circumstances anon-radiopaque composite may be desirable.

The amount of filler which is incorporated into the composite, referredto herein as the "loading level" and expressed as a weight percent basedon the total weight of the dental material, will vary depending on thetype of filler, the epoxy resin and other components of the composition,and the end use of the composite.

For some dental materials, such as sealants, the epoxy resincompositions of the invention can be lightly filled (e.g., having aloading level of less than about 40 weight percent) or unfilled.Preferably the viscosity of the dental material is sufficiently low toallow its penetration into pits and fissures of occlusal tooth surfacesas well as into etched areas of enamel, thereby aiding in the retentionof the dental material. In applications where high strength ordurability are desired (e.g., anterior or posterior restoratives,prostheses, crown and bridge cements, artificial crowns, artificialteeth and dentures) the loading level can be as high as about 95 weightpercent. For most dental restorative and prosthetic applications aloading level of between about 70 and 90 weight percent is generallypreferred.

Fillers may be selected from one or more of any material(s) suitable forincorporation in compositions used for medical applications, such asfillers currently used in dental restorative compositions and the like.The filler is finely divided and preferably has a maximum particlediameter of less than about 50 micrometers and an average particlediameter of less than about 10 micrometers. The filler can have aunimodal or polymodal (e.g., bimodal) particle size distribution. Thefiller can be an inorganic material. It can also be a crosslinkedorganic material that is insoluble in the polymerizable resin, and isoptionally filled with inorganic filler. The filler should in any eventbe non-toxic and suitable for use in the mouth. The filler can beradiopaque, radiolucent or nonradiopaque.

Examples of suitable inorganic fillers are naturally-occurring orsynthetic materials such as quartz, nitrides (e.g., silicon nitride),glasses derived from, for example Ce, Sb, Sn, Zr, Sr, Ba and Al,colloidal silica, feldspar, borosilicate glass, kaolin, talc, titania,and zinc glass; low Mohs hardness fillers such as those described inU.S. Pat. No. 4,695,251; and submicron silica particles (e.g., pyrogenicsilicas such as the "Aerosil" Series "OX 50 ", "130", "150" and "200"silicas sold by Degussa and "Cab-O-Sil M5" silica sold by Cabot Corp.).

Examples of suitable organic filler particles include filled or unfilledpulverized polycarbonates, polyepoxides, and the like. Preferred fillerparticles are quartz, submicron silica, and non-vitreous microparticlesof the type described in U.S. Pat. No. 4,503,169. Metallic fillers mayalso be incorporated, such as particulate metal filler made from a puremetal such as those of Groups IVA, VA, VIA, VIIA, VIII, IB, or IIB,aluminum, indium, and thallium of Group IIIB, and tin and lead of GroupIVB, or alloys thereof Conventional dental amalgam alloy powders,typically mixtures of silver, tin, copper, and zinc, may also optionallybe incorporated. The particulate metallic filler preferably has anaverage particle size of about 1 micron to about 100 microns, morepreferably 1 micron to about 50 microns. Mixtures of these fillers arealso contemplated, as well as combination fillers made from organic andinorganic materials. Fluoroaluminosilicate glass fillers, eitheruntreated or silanol treated, are particularly preferred. These glassfillers have the added benefit of releasing fluoride at the site ofdental work when placed in the oral environment.

Optionally, the surface of the filler particles may be treated with asurface treatment such as a coupling agent in order to enhance the bondbetween the filler and the polymerizable resin. The coupling agent maybe functionalized with reactive curing groups, such as acrylates,methacrylates, epoxies, and the like. Examples of coupling agentsinclude silanes such as gamma-methacryloxypropyltrimethoxysilane,gamma-mercaptopropyltriethoxysilane,beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,gamma-glycidoxypropyltrimethoxysilane, and the like.

The materials of the present invention can also contain suitableadjuvants such as accelerators, inhibitors, absorbers, stabilizers,pigments, dyes, viscosity modifiers, surface tension depressants andwetting aids, antioxidants, and other ingredients well known to thoseskilled in the art.

The amounts and types of each ingredient in the dental material shouldbe adjusted to provide the desired physical and handling propertiesbefore and after cure. For example, the cure rate, cure stability,fluidity, compressive strength, tensile strength and durability of thedental material typically are adjusted in part by altering the types andamounts of polymerization initiator(s) and, if present, the loading andparticle size distribution of filler(s). Such adjustments typically arecarried out empirically based on experience with dental materials of theprior art.

When the dental material is applied to a tooth, the tooth can optionallybe pre-treated with a primer such as dentin or enamel adhesive bymethods known to those skilled in the art.

The invention is further described by reference to the followingexamples, which are understood to be merely illustrative and notlimiting the invention in any way.

EXAMPLE 1

A stock resin solution ("SL1") of an epoxy resin and polyol containingmaterial was prepared by combining 0.50 g camphorquinone, 1.50 gdiphenyliodoniumhexafluoroantimonate (DPI SbF₆) with 24.50 g UVR 6105cycloaliphatic diepoxide and 0.50 g of polytetrahydrofuran diol havingan average molecular weight of 250 (pTHF-250) and stirring untilhomogeneous in the absence of light. UVR 6105 is a cycloaliphaticdiepoxide having the following formula: ##STR5##

A variety of donor compounds were evaluated for their photoinducedpotential and ability to enhance cure speed. To evaluate thephotoinduced potential of the compounds, a stock initiator solution wasprepared by transferring 0.50 grams camphorquinone and 3.00 grams of DPISbF₆ to a 250 ml polyethylene screw-top bottle. Two hundred grams of99.5+% 2-butanone was transferred to the polyethylene bottle and thecontents mixed until homogeneous. The resulting solution containedapproximately 2.9×10⁻⁵ moles DPISbF6/gram and 1.5×10⁻⁵ moles CPQ/gram.The electron donor additives were evaluated at a concentration of2.9×10⁻⁵ moles donor/gram of SL1. Samples were prepared by transferring1.16×10⁻⁴ moles of donor to a 13 ml glass vial followed by the additionof 4.0 grams of the stock initiator solution. Vials were capped andvigorously shaken until homogeneous. Samples were then evaluated forrelative potential according to the following procedure:

A semi-micro combination pH electrode (Corning model 476540) wasconnected to a pH meter with millivolt capability (Beckman Φ P/N123133). The stock initiator solution was used as the millivolt standardin this evaluation. Four grams of the stock initiator solution weretransferred to a 13 ml glass vial along with a micro-magnetic stir bar.The sample was placed above a magnetic stirrer which initiated slowstirring of the sample. The electrode was rinsed with water followed byethanol and then thoroughly dried with a paper towel. The electrode wasimmersed in the stock initiator solution and the millivolt readingcalibrated to read 0.00 mV. The electrode was removed and the sample wasirradiated with a Visilux dental curing light having an intensity ofabout 200 mW/cm² at a wavelength of 400 to 500 nm for 10 seconds byplacing the tip of the light guide directly flush with the center bottomof the vial. Following irradiation the sample was capped and mixedthoroughly by shaking for about 5 seconds. The electrode was rinsed,cleaned thoroughly with ethanol, blotted dry and immersed in theirradiated solution. The millivolts relative to the control wasestablished by pressing the mV button on the pH meter until a stablereading was obtained. The above procedure was repeated with the variousdonor solutions. The electrode was calibrated with unirradiated stockinitiator solution before each run as described previously.

The donor compounds were also evaluated for their effect on cure speedof the stock resin solution. Approximately one gram samples wereprepared by transferring 2.9×10⁻⁵ moles of each prospective donor to 1dram glass vials followed by 1.0 grams of the stock resin solution. Theingredients were mixed until homogeneous. Each sample was examined forgel time by transferring the solution to a 6 mm diameter and 2.5 mmthick Teflon mold with a polyester film clamped in direct contact withthe bottom face. The sample was placed directly beneath the light guideof a Visilux 2 dental curing light at a distance of 10 mm. Samples wereirradiated and probed to establish hard gel times up to a maximum of 60seconds. Results are reported in Table 1. Throughout the examples, "NC"means that the material did not cure and "NT" means that the materialwas not tested.

                                      TABLE 1                                     __________________________________________________________________________    Sample #                                                                           Donor Compound                                                                              gms donor/gm resin                                                                     gel time (sec)                                                                       mv (initial) MEK                                                                      mv (photo) MEK                     __________________________________________________________________________     1   None          none     25     0       -25                                   2 4-dimethylaminobenzoic acid 0.0047  7 -11 184                               3 ethyl 4-dimethylaminobenzoate 0.0053  7 -12 200                             4 3-dimethylaminobenzoic acid 0.0047 12 -5 115                                5 1,2,4-trimethoxybenzene 0.0053  7 -3 233                                    6 4-dimethylaminobenzoin 0.0068  9 -13.4 261                                  7 4-dimethylaminobenzonitrile 0.0045 16 (top) 9.7 266                         8 4-dimethylaminobenzaldehye 0.0043 16 (top) 8 245                            9 4-dimethylaminophenethanol 0.0046 NC -83.2 17                              10 dimethylaniline 0.0043 20 -55 54                                           11 2,5-dimethoxybenzylalcohol 0.0049 25 30.8 52                               12 tetrahydrofurfuralalcohol 0.0030 25 -34 -10                                13 1,2,3-trimethoxybenzene 0.0050 25 -1.9 5                                   14 1,3,5-trimethoxybenzene 0.0050 24 10.1 28                                  15 benzyl alcohol 0.0031 26 -13.7 24                                          16 2,4,6-pentamethylaniline 0.0050 22 10 71.3                                 17 N,N-dimethylbenzylamine 0.0040 25 -189.7 -170                              18 triethanolamine 0.0042 NC -171 -162                                        19 dihydroxyethyl-p-toluidine 0.0058 NC -180 -98                              20 4-t-butyl N,N-dimethylaniline 0.0050 34 NT NT                            __________________________________________________________________________

EXAMPLE 2

A stock solution of an epoxy resin/polyol/acrylate resin material wasprepared by transferring 0.50 g camphorquinone and 1.50 g DPI SbF₆ to aglass jar followed by the addition of approximately 0.20 g ofdichloromethane solvent, 70.56 g of UVR 6105, 9.80 g of Ebecryl 1830polyester hexacrylate (Radcure Specialties) and 17.64 g of pTHF-250. Themixture was stirred until homogeneous in the absence of light.

Three donor compounds were evaluated for photoinduced potential and fortheir ability to enhance the cure speed of the epoxy/polyol/acrylateresin material.

To evaluate the photoinduced potential of the compounds, a stockinitiator solution ("SL2") was prepared by transferring 0.50 gramscamphorquinone and 3.00 grams of DPI SbF₆ to a 250 ml polyethylenescrew-top bottle. Two hundred grams of 99.5+% 2-butanone weretransferred to the polyethylene bottle and the contents mixed untilhomogeneous. The resulting solution contained approximately 2.9×10⁻⁵moles DPISbF6/gram and 1.5×10⁻⁵ moles CPQ/gram. The electron donoradditives were evaluated at a concentration of 2.9×10⁻⁵ moles donor/gramof SL2. Samples were prepared by transferring 1.16×10⁻⁴ moles of donorto a 13 ml glass vial followed by the addition of 4.0 grams of the stockinitiator solution. Vials were capped and vigorously shaken untilhomogeneous. Samples were then evaluated for relative potentialaccording to the procedure detailed in Example 1.

The donor compounds were evaluated for their effect on cure speed of theepoxy/polyol/acrylate resin solution. Approximately one gram sampleswere prepared by transferring 2.9×10⁻⁵ moles of each prospective donorto 1 dram glass vials followed by 1 drop of dichloromethane solvent and1.0 grams of the stock resin material. The ingredients were mixed untilhomogeneous. Each sample was examined for gel time by transferring thesolution to a 6 mm diameter and 2.5 mm thick Teflon mold with apolyester film clamped in direct contact with the bottom face. Thesample was placed directly beneath the light guide of a Visilux 2 dentalcuring light at a distance of 3 cm. Samples were irradiated up to amaximum of 120 seconds and probed to establish soft and hard gel times.Results are reported in Table 2.

                  TABLE 2                                                         ______________________________________                                                                  gel                                                    gms donor/ time Mv Mv                                                        Donor Compound gm resin (sec) (initial) (photo)                             ______________________________________                                        none            none      120    0     -25                                      4-dimethylaminobenzoic acid 0.0047 30 -11 184                                 ethyl 4-dimethylaminobenzoate 0.0053 35 -12 200                               4-dimethylaminobenzoin 0.0068 70 -13 261                                    ______________________________________                                    

EXAMPLE 3

A bifunctional epoxy/acrylate material was prepared according to thefollowing procedure:

Epon 828 Bis Phenol-A-diepoxide (82.9 grams, 0.22 moles) was transferredto 250 ml three-necked resin flask which was fitted with a condenser, anair driven stir rod with a Teflon stir blade and an addition funnel. Thesystem was kept dry with a calcium sulfate drying tube. The resinreactor was partially immersed in an oil bath heated to about 100° C.and the diepoxide allowed to equilibrate to this temperature for about30 minutes. Triphenyl antimony (1.1 grams) was transferred to thediepoxide and allowed to dissolve for about 15 minutes. Methacrylic acid(17.2 grams, 0.20 moles) was weighed into the addition funnel and thenslowly added to the heated diepoxide slowly over about 3 hours. Themixture was allowed to react for a total of 24 hours yielding a highviscosity liquid which comprised a statistical mixture ofmonoepoxide/monomethacrylate adduct and both diepoxide anddimethacrylate.

EXAMPLE 4

Two epoxy/acrylate polyol compositions were prepared from the reactionproduct of example 3 as shown below with and without diphenyliodoniumsalt (DPISbF₆):

    ______________________________________                                                       Sample 1    Sample 2                                             Ingredient Parts by Weight Parts by Weight                                  ______________________________________                                        UVR6105 epoxy  64.00       64.00                                                Product of Example 2 20.00 20.00                                              pTHF-250 16.60 16.60                                                          DPISbF.sub.6 0.00 1.50                                                        CPQ 0.50 0.50                                                                 EDMAB 0.56 0.56                                                             ______________________________________                                    

Samples approximately 2.5 mm thick were irradiated with a Visilux 2Dental curing light from a distance of about 10 mm for about 30 seconds.Both samples were relatively soft and flexible and failed to register aBarCol hardness value. Samples were transferred to an oven at 37° C. for24 hours. Sample 1 remained relatively soft whereas Sample 2 withDPISbF₆ was a hard solid with a barcol hardness value of about 30. Thedata shows that the initial gelation is attributed to the free radicalpolymerization from the reaction product of example 3 and subsequentpolymerization results from cationic curing of the epoxy resin UVR 6105and reaction product of example 3, and that addition of the diphenyliodonium salt or compound provides cationic curing in addition to freeradical curing.

EXAMPLE 5

The effect of various diphenyl iodonium salts was evaluated in epoxyresin/polyol compositions with and without the presence of an aromaticamine. Three epoxy/polyol containing compositions were prepared asfollows:

    ______________________________________                                                       Parts by Weight                                                ______________________________________                                        Composition A(1)                                                                UVR 6105 80.0                                                                 pTHF-250 20.0                                                                 Camphorquinone 0.50                                                           DPI SbF.sub.6 1.50                                                            Composition B(1)                                                              UVR 6105 80.0                                                                 pTHF-250 20.0                                                                 Camphorquinone 0.50                                                           DPI PF.sub.6 1.23                                                             Composition C(1)                                                              UVR 6105 80.0                                                                 pTHF 20.0                                                                     Camphorquinone 0.50                                                           DPI Cl 0.90                                                                 ______________________________________                                    

Ethyl 4-dimethylaminobenzoate (EDMAB) was added to a portion of theabove compositions in an amount of 0.56 parts by weight per 100 parts ofeach of A(1), B(1) and C(1), forming compositions A(2), B(2) and C(2)respectively.

Each composition was prepared by combining the ingredients at roomtemperature and stirring until homogeneous. Each composition wasevaluated for cure speed by irradiation of a 2 mm thick sample withlight at a wavelength of 400-500 nm from a Visilux 2 light source at adistance of 10 mm. Irradiation continued for 120s or until a soft orhard gel was formed. Results are reported in Table 3.

                  TABLE 3                                                         ______________________________________                                        Composition        Gel time (seconds)                                         ______________________________________                                        A(1)               14                                                           B(1) 16                                                                       C(1) NC                                                                       A(2) 8                                                                        B(2) 8                                                                        C(20) NC                                                                    ______________________________________                                    

This data illustrates that enhanced cure speed can be achieved when theamine electron donor EDMAB is used in combination with an iodonium saltwith a ⁻ PF₆ or ⁻ SbF₆ counterion. No curing was observed when ⁻ Cl wasthe counterion, with or without the donor EDMAB.

EXAMPLE 6

A variety of visible light absorbing sensitizers were evaluated inepoxy/polyol formulations containing 1.50% Ph₂ lSbF₆, 0.50% sensitizercompound and optionally 0.56% EDMAB by weight. Solutions A and B,without and with EDMAB respectively were prepared as shown below:

    ______________________________________                                                    Solution A  Solution B                                              Ingredient Parts by Weight Parts by Weight                                  ______________________________________                                        UVR6105     80.00       80.00                                                   pTHF-250 20.00 20.00                                                          DPISbF.sub.6  1.50 1.50                                                       EDMAB -- 0.56                                                               ______________________________________                                    

Sensitizers were evaluated by transferring 0.0050 grams of thesensitizer to a 2 dram glass vial followed by the addition of 2 drops ofdichloromethane solvent and 1.0 grams of solution A. Compositions weremixed until homogeneous and evaluated for gel time as described inexample 1. The same procedure was repeated for solution B. Set out inTable 4 are the run numbers, sensitizer and the gel times with andwithout EDMAB.

                  TABLE 4                                                         ______________________________________                                        Sample               Gel time/no                                                # Sensitizer Compound EDMAB Gel time/EDMAB                                  ______________________________________                                              (0.0050 gm/gm resin)                                                                         (seconds)   (seconds)                                      1 None NC NC                                                                  2 Camphorquinone 14 8                                                         3 2-Chlorothioxanthone 25 (surface only) 15                                   4 Fluorenone NC 30 (top 1 mm)                                                 5 Furil 115 40                                                                6 Dibromofluorescein 70 17                                                    7 Fluorescein 95 (surface only) 91 (surface only)                             8 Ethyl Eosin 64 (surface only) 15                                            9 Eosin y 19 (surface only) 20 (complete                                         cure)                                                                      10 Benzoylbenzocoumarin NC 15                                                 11 Rose Bengal NC 26                                                          12 Isopropylthioxanthone 11 (surface only) 20 (complete                          cure)                                                                      15 Anthraquinone 30 (surface only) 90 (complete                                  cure)                                                                      16 Diethoxyanthracene 20 (surface only) 40 (surface only)                     17 2-ethyl-9,10 22 (surface only) 45 (surface only)                            dimethoxyanthracene                                                          18 9,10 dichloroanthracene NC NC                                              19 Diphenyl isobenzofuran 32 41                                               20 Methylene violet NC NC                                                   ______________________________________                                    

The data illustrates that a variety of ketone functional sensitizers incombination with DPISbF₆ and the electron donor EDMAB photocures fasterand/or more completely than those formulations with sensitizer andDPISbF₆ alone.

EXAMPLE 7

The effect of EDMAB to DPISbF₆ molar ratio on gel time was examined.Molar ratios of EDMAB/DPISbF₆ ranging from 0 to 8.0 were investigated.Solution A was prepared by combining 16.0 g UVR 6105, 4.0 g pThF-250,0.10 g camphorquinone and 0.30 g DPISbF6. This solution contained2.9×10⁻⁵ moles off DPISbF₆ per gram of resin. Solution B was prepared bytransferring 0.44 grams of EDMAB to a glass vial followed by 10.0 gramsof solution A resulting in a formulation containing 2.3×10⁻⁴ moles ofEDMAB per gram of resin or 8 molar equivalents of EDMAB/DPISbF₆. 1 grammixtures of Solutions A and B were prepared and evaluated for gel timeas described in Example 1, however the irradiation distance was 10 mm.Set out in Table 5 are the run numbers, grams of solutions A and B, themolar ratio of amine to onium salt and the gel times.

The data illustrates that significant cure speed enhancement can beachieved with as little as 0.08 equivalents of EDMAB relative to oniumsalt. Optimal cure speed is achieved with approximately 0.10 to 1.0equivalents. Further addition of EDMAB beyond 1.0 equivalents results ina near linear increase in gel time (inhibition) and decrease in materialhardness.

                  TABLE 5                                                         ______________________________________                                              Grams     Grams                                                            solution B solution A                                                         2.32 × 10.sup.-4 2.0 × 10.sup.-5 Molar Ratio Gel                 Sample moles moles EDMAB/ time                                                # EDMAB/gm onium/gm Onium (seconds) Comments                                ______________________________________                                        1     0.00      1.00     0.00    18     hard solid                              2 0.01 0.99 0.08 9 hard solid                                                 3 0.02 0.98 0.16 7 hard solid                                                 4 0.03 0.97 0.25 8 hard solid                                                 5 0.05 0.95 0.40 8 hard solid                                                 6 0.10 0.90 0.80 8 hard solid                                                 7 0.20 0.80 1.60 13 hard solid                                                8 0.30 0.70 2.40 15 hard gel                                                  9 0.40 0.60 3.20 20 hard gel                                                  10 0.50 0.50 4.00 21 hard gel                                                 11 0.60 0.40 4.80 25 soft gel                                                 12 0.70 0.30 5.60 30 soft gel                                                 13 0.80 0.20 6.40 35 soft gel                                                 14 0.90 0.10 7.20 55 soft gel                                                 15 1.00 0.00 8.00 60 soft gel                                               ______________________________________                                    

The data shows that the addition of the amine donor EDMAB can bothenhance and decrease the cure speed and properties based on low and highconcentrations, respectively, relative to the absence of EDMAB

EXAMPLE 8

Eighteen photocurable epoxy/polyol resin formulations were prepared withthe component concentrations as shown in Table 5 for a 2.sup.(5-1)fractional factorial design experiment. The five experimental variablesin the study were:

A) % camphorquinone (CPQ),

B) % diphenyliodonium hexafluoroantiminate (DPISbF6),

C) % ethyl4-dimethyl aminobenzoate (EDMAB),

D) ratio of aliphatic to cycloaliphatic diepoxides (EPON/UVR ratio),

E) % polytetrahydrofuran MW 250 (pTHF).

The aliphatic diepoxide used was diglycidyl ether of bisphenol A (Epon828, Shell Oil Co.); the cycloaliphatic diepoxide used was3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (UVR-6105).

Gel time of each of the prepared resin solutions was tested undercontinuously irradiating of a Visilux-2 dental curing light. Threemillimeter thick cylindrical Teflon BarCol Hardness molds were filledwith uncured resin. The uncured resin in each mold was then irradiatedat a distance of 1 cm with a Visilux-2 dental curing light while beingfrequently probed with a plastic mixing stick. The time in seconds atwhich the resin began to thicken and exhibit properties of a soft solidwas recorded as gel time. The average of three such tests for each resinformulation is tabulated in Table 6 alongside the correspondingcompositional information for each resin formulation.

The statistical analysis (YATES ANOVA) indicates that EDMAB was astatistically significant variable with an average effect of 7.7 secondsreduction in gel time when 1 molar equivalent (based on DPISbF6) isadded to the resin formulations.

                                      TABLE 6                                     __________________________________________________________________________    VISIBLE LIGHT CURED EPOXY FORMULATIONS                                          WITH DPISbF.sub.6 IN EPOXY/POLYOL RESIN                                     __________________________________________________________________________                          2(5-1) Fractional Factorial                             Resin Variables                                                                             Variable                                                                              (-)  0    (+)                                           __________________________________________________________________________      % Camphorquinone Sensitizer 0.25% 0.50% 0.75                                  % DPISbF6 (CD-1012) Catalyst 0.50% 1.00% 2.00%                                EDMAB (DPISbF6) equiv.) Electron donor (0 eq.) (0.5 eq.) (1 eq.)                                             EPON 828:UVR-6105 Ratio Epoxy resins 1:2                                     1:1 2:1                                         % Polytetrahydrofuran Polyol 10% 20% 30%                                    __________________________________________________________________________    1 equiv. EDMAB = Grams DPISbF6 (193/516)                                           mol. wt. EDMAB = 193                                                                     mol. wt. DPISbF6 = 516                                        __________________________________________________________________________    WEIGHT PERCENT OF COMPONENTS IN ACTIVATED RESIN                                                  EPON     pTHF                                                                              GEL                                             DESIGN CPQ DBISbF6 EDMAB 828 UVR6105 (250) TIME                               ORDER (grams) (grams) (grams) (grams) (grams) (grams) (seconds)             __________________________________________________________________________       1 0.25 0.50 0.00 23.08 46.17 30.00 14.3                                       2 0.75 0.50 0.00 29.58 59.17 10.00 24.0                                       3 0.25 2.00 0.00 29.25 58.50 10.00 46.0                                       4 0.75 2.00 0.00 22.42 44.83 30.00 14.0                                       5 0.25 0.50 0.19 29.69 59.37 10.00 12.6                                       6 0.75 0.50 0.19 22.85 45.71 30.00 11.0                                       7 0.25 2.00 0.75 22.33 44.67 30.00 18.0                                       8 0.75 2.00 0.75 28.83 57.67 10.00 13.3                                       9 0.25 0.50 0.00 59.50 29.75 10.00 37.3                                      10 0.75 0.50 0.00 45.83 22.92 30.00 23.0                                      11 0.25 2.00 0.00 45.17 22.58 30.00 23.6                                      12 0.75 2.00 0.00 58.17 29.08 10.00 39.0                                      13 0.25 0.50 0.19 46.04 23.02 30.00 30.6                                      14 0.75 0.50 0.19 59.04 29.52 10.00 17.6                                      15 0.25 2.00 0.75 58.00 29.00 10.00 26.6                                      16 0.75 2.00 0.75 44.33 22.17 30.00 30.0                                      17 0.50 1.00 0.19 39.15 39.16 20.00 11.3                                      18 0.50 1.00 0.19 39.16 39.15 20.00 11.3                                    __________________________________________________________________________    Response: GEL TIME                                                            VAR    VARIABLE                                                                            UNITS   -1 LEVEL                                                                            +1 LEVEL                                           __________________________________________________________________________      A CPQ % 0.250 0.750                                                           B DPISbF6  -0.301 0.301                                                       C EDMAB  0.000 1.000                                                          D 828:UVR  0.333 0.666                                                        E pTHF % 10.000 30.000                                                      __________________________________________________________________________                      STANDARDIZED                                                                           SUM OF                                               VARIABLE COEFFICIENT EFFECT SQUARES                                           OVERALL 22.42                                                                 AVERAGE                                                                     __________________________________________________________________________      A -2.32 -4.64 86.0                                                            B 2.51 5.01 100.5                                                             C -3.84 -7.69 236.4                                                           D 4.66 9.31 346.9                                                             E -3.24 -6.49 168.4                                                           AB 0.08 0.16 0.1                                                              AC 0.33 0.66 1.8                                                              AD 1.26 2.51 25.3                                                             AE 1.26 2.51 25.3                                                             BC -0.49 -0.99 3.9                                                            BD -1.17 -2.34 21.9                                                           BE -1.67 -3.34 44.6                                                           CD 1.58 3.16 40.0                                                             CE 5.68 11.36 516.4                                                           DE 1.58 3.16 40.0                                                             CENTER POINT -12.51  278.1                                                  __________________________________________________________________________

EXAMPLE 9 (PREPARATIVE EXAMPLE)

200.3 grams of deionized water was weighed into a 1000 ml rigid polybeaker and adjusted to a pH of 3.02 with trifluoroacetic acid (AldrichChem. Co., Milwaukee, Wis.). 9.9099 grams of3-glycidoxypropyltrimethoxysilane (United Chemical Technologies, Inc.,Bristol, Pa.) was slowly added to the water while stirring with amagnetic Teflon coated stirring rod. About 50 ml of denatured ethanolwas used to rinse the silane addition beaker, and then added to thehydrolyzing aqueous silane solution. The solution was allowed to stirfor about 65 minutes (hydrolysis time) and then 200 grams of a 90/10weight blend of ball mill ground mined quartz, average particle size2.25-3.15 microns (3M Co., Maplewood, Minn., PMC41-5300-0422-9) and acommercially available fumed silica, Aerosil OX-50 (Degussa Inc.,Frankfurt, GE) was slowly added to the silane treatment solution. Theresulting slurry was stirred for 27 hours at room temperature. Theslurry was then divided evenly among three 1000 ml poly beakers eachbeaker placed in a convection drying oven for 12 hours at 60° C. Thedried cake from each beaker was recombined, mortar and pestled, and thenscreen in a sealed container on a shaker through a 74 micron nylonscreen. The screened powder was then placed in a one pint jar and driedfor a final time for 2 hours at 80° C. After a short cool down the jarwas then sealed with a metal cap with foil lined paper seal to reducethe moisture vapor transmission into or out of the jar.

EXAMPLE 10

This example describes the preparation of epoxy/polyol resin-basedcomposite materials containing an iodonium salt, an alpha-diketone andan optional amine electron donor (EDMAB).

Two compositions were prepared as follows:

    ______________________________________                                        Composition A                                                                   UVR 6105 8.00 g                                                               pTHF250 2.00 g                                                                DPI SbF6 0.15 g                                                               Camphorquinone (CPQ) 0.05 g                                                   Total 10.20 g                                                                 Composition B                                                                 UVR 6105 8.00 g                                                               pTHF250 2.00 g                                                                DPI SbF6 0.15 g                                                               CPQ 0.05 g                                                                    EDMAB 0.05 g                                                                  Total 10.20 g                                                               ______________________________________                                    

Each composition was prepared by combining the ingredients at roomtemperature and stirring until homogeneous.

Two composite materials were further prepared by combining 7.50 grams ofthe filler from Example 9 with 2.50 grams of Compositions A and Brespectively. Samples were spatulated until a thick homogeneous pastewas obtained

    ______________________________________                                        Composite A                                                                     Composition A 2.50 g                                                          Filler from Example 9 7.50 g                                                  Total 10.00 g                                                                 Composite B                                                                   Composition B 2.50 g                                                          Filler from Example 9 7.50 g                                                  Total 10.00 g                                                               ______________________________________                                    

Samples were evaluated for photopolymerization by determining the BarColA hardness of 2 mm thick sample according to the following procedure. A2 mm thick Teflon block which had a cylindrical hole with a diameter ofabout 6 mm that extended through the thickness of the block was placedon a film of transparent polyethylene terephthalate (PET) such that oneend of the of the open cylindrical hole of the die was covered by thePET film. The Teflon die was filled with the sample and another film ofPET placed on top of the die covering paste sample. Hand pressure wasapplied to the PET film to provide an approximately 2 mm thick sample,samples were irradiated with the Visilux 2 light source for 30 secondsby placing the light wand directly on the PET film which covered thesample at the top of the die. Five sets of samples were prepared intriplicate and stored at for 5 minutes, 20 minutes and 24 hours at 25°C. and 20 minutes and 24 hours at 37° C. respectively, after storage,the PET films were removed and the BarCol hardness of the top and bottomof the die was measured using a Barber-Coleman Impressor (a hand-heldportable hardness tester; Model GYZJ 934-1; from Barber Coleman CompanyIndustrial Instruments Division, Lovas Park, Ind.) equipped with anindenter. For each sample tested, three readings were taken at the topand bottom of each sample. The readings were averaged for eachcomposition and storage condition. A hardness value of zero indicatedlimited or no polymerization. Bottom hardness values significantly lessthan those of the top indicate limited depth of cure. Results aresummarized in Table 7 below:

                  TABLE 7                                                         ______________________________________                                                         Barcol Hardness                                                               25° C.   37° C.                                         Side                  24          24                                   Sample Tested 5 min. 20 min. hours 20 min. hours                            ______________________________________                                        Composite A                                                                            Top     48      58    67    66    70                                   (no EDMAB) Bottom 18 40 67 62 67                                              Composite B Top 54 54 56 64 56                                                (EDMAB) Bottom 52 53 63 67 63                                               ______________________________________                                    

The data shows that Composite B which contains the donor EDMAB exhibitsgreater top and bottom hardness when post-cured for 5 minutes at 25° C.,compared to Composite A without EDMAB. This illustrates that theco-catalyst EDMAB significantly enhances the rate of curing of theepoxy/polyol composite.

EXAMPLE 11

This example describes the preparation of epoxy/polyol/methacrylateresin-based composite materials containing an iodonium salt, analpha-diketone and an optional amine electron donor.

Two compositions were prepared as follows:

    ______________________________________                                        Composition A                                                                   UVR 6105 7.20 g                                                               pTHF250 1.80 g                                                                Ebercryl 1830 1.00 g                                                          DPISbF6 0.15 g                                                                Camphorquinone 0.05 g                                                         Total 10.20 g                                                                 Composition B                                                                 UVR 6105 7.20 g                                                               pTHF250 1.80 g                                                                Ebecryl 1830 1.00 g                                                           DPISbF6 0.15 g                                                                Camphorquinone 0.05 g                                                         ethyl-p-dimethylaminobenzoate 0.05 g                                          Total 10.25 g                                                               ______________________________________                                    

Each composition was prepared by combining the ingredients at roomtemperature and stirring until homogeneous.

Two composite materials were further prepared by combining 7.50 grams ofthe filler from Example 9 with 2.50 grams of Compositions A and Brespectively. Samples were spatulated until a thick homogeneous pastewas obtained

    ______________________________________                                        Composite A                                                                     (no EDMAB)                                                                    Composition A 2.50 g                                                          Filler from Example 9 7.50 g                                                  Total 10.00 g                                                                 Composite B                                                                   (EDMAB)                                                                       Composition B 2.50 g                                                          Filler from Example 9 7.50 g                                                  Total 10.00 g                                                               ______________________________________                                    

Samples were evaluated for photopolymerization by determining the BarColA hardness of 2 mm thick sample according to the procedure described inExample 9. Results are summarized in Table 8 below.

                  TABLE 8                                                         ______________________________________                                                         Barcol Hardness                                                               25° C.   37° C.                                         Side                  24          24                                   Sample Tested 5 min. 20 min. hours 20 min. hours                            ______________________________________                                        Composite A                                                                            Top     45      39    66    58    70                                   (no EDMAB) Bottom 0 0 58 17 59                                                Composite B Top 47 54 64 60 64                                                (EDMAB) Bottom 37 53 64 59 59                                               ______________________________________                                    

The data shows that Composite B which contains the donor EDMAB exhibitssignificantly greater bottom polymerization when post-cured for 5 or 20more minutes at 25° C. or 20 minutes at 37° C., compared to Composite Awithout EDMAB. The electron donor EDMAB provides enhanced cure speedsfor thick sections of epoxy/polyol/acrylate composites.

EXAMPLE 12

Dental restorative pastes were prepared from each of the five lightcurable epoxy/polyol resin formulations shown in Table 8. The filler foreach was prepared from a blend of 95 wt % finely milled P-10™ quartzfiller (¹⁸ 3 micron APS) and 5 wt % fumed silica OX-50 (Degussa Inc.).The two silica based filler were blended in a 1000 ml beaker, thenslurred overnight in a 3-3.5 pH hydrolyzed aqueous solution of 5% (basedon filler weight) 3-glycidoxypropyltrimethoxy silane. The slurry cakewas dried at 60° C. for 12 hours, crushed and screened through a 74micron nylon screen. After a final drying of 80° C. for two hours thefiller was hand spatulated into the resins in 8-10 gram batch sizes toeither 82.0% or 82.5% filler weight loading.

The resulting pastes were then tested for compressive strength anddiametral tensile strength after irradiation with two Visilux-2 dentalcuring lights for 80 seconds in 1/8" ID Lexan tubing and after a postcure of 24 hours in 37° C. distilled water.

                                      TABLE 9                                     __________________________________________________________________________    LIGHT CURED EPOXY FORMULATIONS                                                  WITH DPISbF6 IN EPOXY/POLYOL RESIN                                                                    Compressive                                                                         Diametral                                       WEIGHT OF COMPONENTS PER 100 GRAM Strength Tensile Wt. %                                  EPON                                                                              UVR-                                                                              pTHF                                                                              (MPa) (MPa)                                                                              Silane                                     CPQ DPISbF6 EDMAB 828 6105 (250) 24 hr. 24 hr. treated                        (grams) (grams) (grams) (grams) (grams) (grams) (n = 5)* (n = 5)*           __________________________________________________________________________                                         Quartz                                   0.75                                                                              0.50 0.00 30.00                                                                             60.00                                                                             10.00                                                                             247 (10)                                                                            69.5 (1.8)                                                                         82.0                                       0.25 0.50 0.00 60.0 30.00 10.00 233 (11) 60.7 (8.6) 82.0                      0.75 2.00 0.75 53.33 26.67 20.00 259 (7) 70.2 (5.0) 82.0                      0.50 1.00 0.19 42.50 42.50 15.00 262 (6) 75.6 (1.7) 82.0                      0.50 1.00 0.19 42.50 42.50 15.00 312 (7) 82.7 (9.4) 82.5                    __________________________________________________________________________     *Numbers in () are standard deviations of 5 test values (n).             

EXAMPLE 13 (PREPARATIVE EXAMPLE)

A bifunctional aliphatic epoxy/acrylate material was prepared accordingto the following procedure:

UVR 6105 Cycloalophatic diepoxide (109.6 grams, 0.44 moles) wastransferred to 250 ml three-necked resin flask which was fitted with acondenser, an air driven stir rod with a Teflon stir blade and anadditional funnel. The system was kept dry with a calcium sulfate dryingtube. The resin reactor was partially immersed in an oil bath heated toabout 100C and the diepoxide allowed to equilibrate for about 30minutes. Triphenyl antimony (0.3 grams) was transferred to the diepoxideand allowed to dissolve for about 15 minutes. Methacrylic acid (8.6grams, 0.11 moles) was weighed into the addition funnel and then slowlyadded to the heated diepoxide slowly over about 3 hours. The mixture wasallowed to react for a total of 24 hours yielding a liquid somewhathigher in viscosity than the starting materials. The bifunctionalepoxy/acrylate material therefore had about one fourth (1/4) of theepoxy functionalities reacted with the unsaturated acid. The resultingresin is referred to hereinbelow as "UVR 1/4."

EXAMPLE 14

This example describes the preparation of twenty-one epoxy/methacrylateresin-based composite materials containing varying amounts of UVR 1/4(described in example 13). UVR6105 (cycloaliphatic diepoxide), pTHF250(aliphatic diol), HPMA (3-hydroxypropyl methacrylate), DPISbF₆ (aniodonium salt), CPQ (camphorquinone--an alpha-diketone) and EDMAB(ethyl-p-dimethyl aminobenzoate--an amine electron donor).

Twenty-one resin compositions were prepared as follows shown in Table10. Each composition was prepared by combining the ingredients at roomtemperature and stirring until homogeneous.

Twenty-one composite materials were further prepared by combining 3.0grams of the quartz filler OX-50 with 6.0 grams of Compositions in Table10 respectively. Samples were spatulated until a thick homogeneous pastewas obtained.

Samples were evaluated for photopolymerization by determining the BarColA hardness of 2 mm thick sample according to the following procedure. A2 mm thick Teflon block which had a cylindrical hole measuring about 6mm diameter that extended through the thickness of the block was placedon a film of transparent polyethylene terphtalate (PET) such that oneend of the open cylindrical hole of the die was covered by the PET film.The Teflon die was filled with the sample and another film of PET placedon top of the die covering paste sample. Hand pressure was applied tothe PET film to provide an approximately 2 mm thick sample. Samples wereirradiated with the Visilux 2 light source for 60 seconds by placing thelight wand directly on the PET film which covered the sample at the topof the die. Three sets of samples were prepared in triplicate and storedfor 10 minutes and 24 hours at 25C. and 24 hours at 37° C. respectively.After storage, the PET films were removed and the hardness of the topand bottom of the die was measured using a Barber-Coleman Impressor (ahand-held portable hardness tester; Model GYZJ 934-1; from BarberColeman Company Industrial Instruments Division, Lovas Park, Ind.)equipped with an indenter. For each sample tested, three readings weretaken at the top and bottom of each sample. The readings were averagedfor each composition and storage condition. A hardness value of zeroindicated limited or no polymerization. Bottom hardness valuessignificantly less than those of the top indicate limited depth of cure.Results are summarized in Table 10 below.

                                      TABLE 10                                    __________________________________________________________________________                                         Barcol Hardness Testing                  Composition of Samples               10 min RT                                                                          24 hr RT                                                                           24 hr 37C                      Sample #                                                                           UVR 1/4                                                                            UVR6105                                                                            pTHF250                                                                            HPMA                                                                              CPQ                                                                              DPISbF.sub.6                                                                       EDMAB                                                                              top/bottom                                                                         top/bottom                                                                         top/bottom                     __________________________________________________________________________    a    1.82 7.58 0.50 0.10                                                                              0.05                                                                             0.125                                                                              0.01 33/0 66/56                                                                              44/33                            b 7.58 1.62 0.50 0.10 0.05 0.125 0.01 0/0 36/24 52/46                         c 1.54 6.38 1.74 0.34 0.05 0.125 0.01 53/52 59/50 37/55                       d 6.38 1.54 1.74 0.34 0.05 0.125 0.01 57/53 57/54 57/59                       e 1.82 7.58 0.33 0.26 0.05 0.125 0.01 62/57 40/57 63/62                       f 7.58 1.82 0.33 0.26 0.05 0.125 0.01 0/0 47/19 56/56                         g 1.52 6.38 1.15 0.93 0.05 0.125 0.01 48/32 54/48 57/57                       h 6.38 1.53 1.15 0.93 0.05 0.125 0.01 27/26 51/32 58/56                       I 4.29 4.30 0.99 0.47 0.05 0.125 0.01 17/0  55/51 52/58                       j 4.29 4.30 0.93 0.47 0.05 0.125 0.01 38/19 53.46 59/61                       k 4.29 4.30 0.93 0.47 0.05 0.125 0.01 20/0  51/43 58/57                       l 4.29 4.30 0.93 0.47 0.05 0.125 0.01 16/0  52/50 59/58                       m 0.00 8.80 0.93 0.47 0.05 0.125 0.01 55/45 53/60 63/61                       n 6.60 0.00 0.93 0.47 0.05 0.125 0.01 0/0 43/44 55/57                         o 5.00 5.00 0.00 0.00 0.05 0.125 0.01 0/0 26/17 51/49                         p 3.77 3.77 1.64 0.82 0.05 0.125 0.01 52/30 54/53 59/59                       q 4.30 4.90 1.40 0.00 0.05 0.125 0.01 55/50 52/56 57/57                       r 4.30 4.30 0.70 0.70 0.05 0.125 0.01 0/0 41/43 55/53                         s 4.30 4.30 0.83 0.47 0.05 0.125 0.01 18/0  44/95 54/54                       t 4.30 4.90 0.99 0.47 0.05 0.125 0.01 34/28 39/39 57/54                       u 0.00 8.00 2.00 0.00 0.05 0.125 0.01 63/54 61/62 65/63                     __________________________________________________________________________

This example demonstrates that compositions containing bifunctionalepoxy/acrylate materials and/or difunctional epoxy materials, andoptionally containing hydroxy functional acrylates, together withpolyols, provide resins that exhibit desirable cure properties. Thesecompositions exhibit either good initial cure properties or demonstratea "living" cure system by hardening over time after initial exposure.

The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. The United States patents referred to in the foregoingspecification are incorporated into the specification by reference.Since many embodiments of the invention can be made without departingfrom the spirit and scope of the invention, the invention resides in theclaims hereinafter appended.

We claim:
 1. A photopolymerizable composition comprising:(a) an epoxyresin; (b) a hydroxyl-containing material; and (c) a photoinitiatorsystem comprising:(i) an iodonium salt; (ii) a visible light sensitizer;and (iii) an electron donor compound, wherein the photoinitiator systemhas a photoinduced potential greater than or equal to that of3-dimethylamino benzoic acid in a standard solution of 2.9×10⁻⁵ moles/gdiphenyl iodonium hexafluoroantimonate and 1.5×10⁻⁵ moles/gcamphorquinone in 2-butanone.
 2. The composition of claim 1 wherein thedonor compound is described by the following structural formula:##STR6## wherein R¹ are independently H; C₁₋₁₈ alkyl that is optionallysubstituted by one or more halogen, --CN, --OH, --SH, C₁₋₁₈ alkoxy,C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl, COOH, COOC₁₋₁₈ alkyl, (C₁₋₁₈alkyl)₀₋₁ -CO--C₁₋₁₈ alkyl, or SO₃ R² ; or aryl that is optionallysubstituted by one or more electron withdrawing groups, where R² is H;C₁₋₁₈ alkyl that is optionaly substituted by one or more halogen, --CN,--OH, --SH, C₁₋₁₈ alkoxy, C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl, COOH,COOC₁₋₁₈ alkyl, (C₁₋₁₈ alkyl(₀₋₁ -CO--C₁₋₁₈ alkyl, or SO₃ H,; or R¹ isaryl that is optionally substituted by one or more electron withdrawinggroups; or the R¹ groups together may form a ring; and Ar is aryl thatis substituted by one or more electron withdrawing groups.
 3. Thecomposition of claim 2 wherein the aryl group is substituted by one ormore carboxylic acid, carboxylic acid ester, ketone, aldehyde, sulfonicacid, sulfonate, or nitrile groups.
 4. The composition of claim 2wherein the aryl group is substituted by one or more moieties selectedfrom the group consisting of --COOH, --COOC₁₋₁₈ alky, --SO₃ R², --CN,--CO--C₁₋₁₈ alkyl and --C(O)H groups, where R² is H, C₁₋₁₈ alkyl that isoptionally substituted by one or more halogen, --CN, --OH, --SH, C₁₋₁₈alkoxy, C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl, COOH, COOC₁₋₁₈ alkyl,(C₁₋₁₈ alkyl)₀₋₁ --CO--C₁₋₁₈ alkyl, SO₃ H, CN or halogen groups, or arylthat is optionally substituted by one or more electron withdrawinggroups.
 5. The composition of claim 1 wherein the donor compound isselected from the group consisting of 4-dimethylaminobenzoic acid, ethyl4-dimethylaminobenzoate, 3-dimethylaminobenzoic acid,4-dimethylaminobenzoin, 4-dimethylaminobenzaldehyde,4-dimethylaminobenzonitrile and 1,2,4-trimethoxybenzene.
 6. Thecomposition of claim 1 wherein the donor compound is an alkyl, arylpolyether.
 7. The composition of claim 1 wherein the donor compound isan alkyl, aryl polyether having the structural formula: ##STR7## whereinn=1-3 each R₃ is independently H or C₁₋₁₈ alkyl that is optionallysubstituted by one or more halogen, --CN, --OH, --SH, C₁₋₁₈ alkoxy,C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl, substituted aryl, --COOH,--COOC₁₋₁₈ alkyl, --(C₁₋₁₈ alkyl)₀₋₁ -COH, --(C₁₋₁₈ alkyl)₀₋₁ CO--C₁₋₁₈alkyl, --CO--C₁₋₁₈ alkyl, --C(O)H or --C₂₋₁₈ alkenyl groups, or the R³groups together may form a ring and each R₄ can be C₁₋₁₈ alkyl that isoptionally substituted by one or more halogen, --CN, --OH, --SH, C₁₋₁₈alkoxy, C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl, substituted aryl,--COOH, --COOC₁₋₁₈ alkyl, --(C₁₋₁₈ alkyl)₀₋₁ -COH, --(C₁₋₁₈ alkyl)₀₋₁-CO--C₁₋₁₈ alkyl, --CO--C₁₋₁₈ alky, C(O)H or --C₂₋₁₈ alkenyl groups. 8.The composition of claim 1 wherein the iodonium salt is an aryl iodoniumsalt.
 9. The composition of claim 1 wherein the iodonium salt comprisesdiphenyliodonium chloride, diphenyl iodonium hexafluorophosphate,diphenyl iodonium hexafluoroantimonate, diphenyl iodoniumtetrafluoroborate, or a mixture thereof.
 10. The composition of claim 1wherein the sensitizing compound comprises a ketone.
 11. The compositionof claim 1 wherein the sensitizing compound comprises an alphadiketone.12. The composition of claim 1 wherein the sensitizing compoundcomprises a ketocoumarin, aminoarylketone, or a para-substitutedaminostyrylketone compound.
 13. The composition of claim 1 wherein thesensitizing compound comprises camphorquinone.
 14. The composition ofclaim 1 wherein the composition cures to a tack-free gel within 60seconds after exposure to visible light.
 15. The composition of claim 1wherein the epoxy resin comprises a cycloaliphatic epoxide or diepoxide.16. The composition of claim 1 wherein the epoxy resin comprises abisphenol-A diepoxide.
 17. The composition of claim 1 wherein the epoxyresin contains ethylenic unsaturation.
 18. The composition of claim 1further comprising an ethylenically unsaturated compound.
 19. Thecomposition of claim 16 wherein the ethylenically unsaturated compoundis an ester of acrylic acid or methacrylic acid.
 20. The composition ofclaim 16 wherein the ethylenically unsaturated compound comprises methylacrylate, methyl methacrylate, ethyl acrylate, isopropyl methacrylate,n-hexyl acrylate, stearyl acrylate, allyl acrylate, glycerol diacrylate,glycerol triacrylate, ethyleneglycol diacrylate, diethyleneglycoldiacrylate, triethyleneglycol dimethacrylate, 1,3-propanedioldiacrylate, 1,3-propanediol dimethacrylate, trimethylolpropanetriacrylate, 1,2,4-butanetriol trimethacrylate, 1,4-cyclohexanedioldiacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate,pentaerythritol tetramethacrylate, sorbitol hexacrylate or a mixturethereof.
 21. A photopolymerizable composition comprising:(a) an epoxyresin; (b) a hydroxyl-containing material; and (c) a photoinitiatorsystem comprising:(i) a diaryliodonium hexafluoroantimonate ordiaryliodonium hexafluorophosphate; (ii) camphorquinone and (iii) anelectron donor described by the following structural formula: ##STR8##wherein R¹ are independently H; C₁₋₁₈ alkyl that is optionallysubstituted by one or more halogen, --CN, --OH, --SH, C₁₋₁₈ alkoxy,C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl, COOH, COOC₁₋₁₈ alkyl, (C₁₋₁₈alkyl)₀₋₁ -CO--C₁₋₁₈ alkyl, or SO₃ R² ; or aryl that is optionallysubstituted by one or more electron withdrawing groups; where R² is H;C₁₋₁₈ alkyl that is optionally substituted by one or more halogen, --CN,--OH, --SH, C₁₋₁₈ alkoxy, C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl, COOH,COOC₁₋₁₈ alkyl, (C₁₋₁₈ alkyl)₀₋₁ -CO--C₁₋₁₈ alkyl, or SO₃ H,; or R¹ isaryl that is optionally substituted by one or more electron withdrawinggroups; or the R¹ groups together may form a ring; and Ar is aryl thatis substituted by one or more electron withdrawing groups.
 22. Aphotopolymerizable composition comprising:(a) an epoxy resin; (b) ahydroxyl-containing material; and (c) a photoinitiator systemcomprising:(i) a diaryliodonium hexafluoroantimonate or diaryliodoniumhexafluorophosphate; (ii) camphorquinone and (iii) an electron donordescribed by the following structural formula: ##STR9## wherein n=1-3each R₃ is independently H or C₁₋₁₈ alkyl that is optionally substitutedby one or more halogen, --CN, --OH, --SH, C₁₋₁₈ alkoxy, C₁₋₁₈ alkylthio,C₃₋₁₈ cycloalkyl, aryl, substituted aryl, --COOH, --COOC₁₋₁₈ alkyl,--(C₁₋₁₈ alkyl)₀₋₁ -COH, --(C₁₋₁₈ alkyl₀₋₁ -CO--C₁₋₁₈ alkyl, --CO--C₁₋₁₈alkyl, --C(O)H or --C₂₋₁₈ alkenyl groups, or the R³ groups together mayform a ring and each R₄ can be C₁₋₁₈ alkyl that is optionallysubstituted by one or more halogen, --CN, --OH, --SH, C₁₋₁₈ alkoxy,C₁₋₁₈ alkylthio, C₃₋₁₈ cycloalkyl, aryl, substituted aryl, --COOH,--COOC₁₋₁₈ alkyl, --(C₁₋₁₈ alkyl)₀₋₁ -COH, --(C₁₋₁₈ alkyl)₀₋₁ -CO--C₁₋₁₈alkyl, --CO--C₁₋₁₈ alkyl, --C(O)H or --C₂₋₁₈ alkenyl groups.
 23. Amethod for photopolymerization comprising the step of irradiating aphotopolymerizable composition with light having a wavelength betweenabout 400 and 1000 nanometers until said composition gels or hardens,said composition comprising:(a) an epoxy resin; (b) ahydroxyl-containing material; and (c) a photoinitiator system, saidphotoinitiator system comprising:(i) an iodonium salt; (ii) a visiblelight sensitizer; and (iii) an electron donor compound, wherein thephotoinitiator system has a photoinduced potential of at least about 100mV relative to a standard solution of 2.9×10⁻⁵ moles per gramdiphenyliodonium hexafluoroantimonate and 1.5×10⁻⁵ moles per gramcarnphorquinone in 2-butanone.
 24. The method of claim 23 wherein thecomposition additionally comprises an ethylenically unsaturatedcompound.
 25. A photopolymerizable dental composition comprising:(a) anepoxy resin; (b) a hydroxyl-containing material; and (c) aphotoinitiator system comprising:(i) an iodonium salt; (ii) a visiblelight sensitizer; and (iii) an electron donor compound, wherein thephotoinitiator system has a photoinduced potential of at least about 100mV relative to a standard solution of 2.9×10⁻⁵ moles/g diphenyl iodoniumhexafluoroantimonate and 1.5×10⁻⁵ moles/g camphorquinone in 2-butanone.26. A composition of claim 25, wherein said composition is a dentaladhesive composition.
 27. A composition of claim 25, wherein saidcomposition is a dental composite material composition.
 28. Acomposition of claim 25, wherein said composition is a dental sealantcomposition.
 29. A composition of claim 25, wherein said composition isan orthodontic adhesive composition.
 30. A composition of claim 1,wherein said composition is a graphic arts imaging composition.
 31. Acomposition of claim 1, wherein said composition is selected from thegroup consisting of photoresist compositions, solder mask compositionselectronic conformal coating compositions, coated abrasive compositionsand magnetic media compositions.